The writing point of a tube writing pen usually consists of a plastic cylindrical member traversed from end to end by a channel for the passage therethrough of ink from an ink reservoir at the end of the channel remote from the writing end of the point, and a cleaning wire, which is attached to a drop weight, and which extends into the channel. A metal writing tube is then attached to the front end of the cylindrical member, usually by being fitted into the cylindrical member, so that it is coaxially aligned with the channel for the ink.
The writing tubes are usually produced by machining a blank of metal tubing on a lathe, the free end of the tubular blank being first face machined, the leading edge being rounded off and an ink step being then turned into the tube material. A length of the tube is then cut off, according to the length of the writing tube that is required, and the face of the "writing tube" thus produced may be submitted to a surface treatment. In order to provide the writing tube with adequate hardness it is generally also hard chromium plated.
The finished writing tube is then fitted into, or within, the cylindrical body for instance by imparting a vibratory motion to the tube.
This method of producing a writing tube and of securing it to a cylindrical member is complicated and costly, firstly because the starting material that must be used, the thin metal tubing, is rather expensive and secondly because a machining operation is necessary which must then be followed by a hard chromium-plating operation step.